Using an existing experiment we have demonstrated in a pilot study that superfluid 3He at 100 μK can be used as a nuclear recoil detector sensitive to neutron and γ interactions depositing energies down to a few hundred eV. The deposited energy is converted to 3He quasiparticles which are detected by their damping effect on a vibrating wire resonator in the liquid. The system can be calibrated independently but a convenient fixed point is provided by the exothermic reaction n+H23e=p+H13+764 keV. Given the great potential for improvement we propose that the system might make a sensitive weakly interacting massive particle detector.

• Received 26 January 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.1887